Measuring Local Condensation Heat Transfer Coefficients In Cryogenic Conditions
Résumé
Condenser-reboilers are key for the efficiency of air distillation processes. In our industry, the boiling side has historically been the limiting factor, and thus most studies have focused on this aspect. This is not necessarily the case anymore, which prompted research efforts on the condensation side.
We present here a novel experimental set up, designed to study the condensation of nitrogen on an aluminum surface (100 mm*200 mm) in cryogenic conditions (-196°C, 1 bar). The cooling power is provided by boiling liquid nitrogen at lower pressure.
One peculiarity of the test bench is its ability to measure local condensation heat transfer coefficients (which have been decoupled from the boiling side). This requires very accurate temperature measurements in order to determine local heat fluxes and surface temperatures. In the present communication, we focus on this experimental aspect. As an illustration, we present data on the condensation performance of a flat plate, which compares favorably with Nusselt theory for subcooling temperatures higher than 0.3°C.